Selumetinib: Uses, Mechanism, and Side Effects

Introduction

Selumetinib is a medicine used to help children with a rare health condition called neurofibromatosis type 1 (Selumetinib NF1). NF1 is uncommon; only about 1 in every 2,500 people has it, and it usually shows up during childhood. This condition causes slow-growing lumps or bumps along the nerves in the body. These bumps are not cancer, but can grow and sometimes cause pain or other problems. Doctors have long looked for a good treatment, and in April 2020, Selumetinib became the first medicine approved to help children with NF1 when surgery isn’t an option.

What Is Neurofibromatosis?

Neurofibromatosis is a genetic disorder that causes the formation of tumors on the nerve tissue. These tumors can be formed anywhere in the nervous system, such as the spinal cord and the nerves. There are three types of neurofibromatosis: neurofibromatosis 1, neurofibromatosis 2, and schwannomatosis. Neurofibromatosis 1 is usually diagnosed in childhood, whereas schwannomatosis and neurofibromatosis 2 are diagnosed in early adulthood. The tumors formed in this disorder are generally non-cancerous (benign), but in some rare cases, they can turn malignant. The treatment of neurofibromatosis should be focused on encouraging healthy growth and development in the patient, as the children affected by this disorder need early management of the complications.

For Patients

What Is Selumetinib?

Selumetinib is a medicine used to treat neurofibromatosis type 1, a genetic disorder that causes tumors to grow along nerves in the body, such as in the skin and brain. These tumors are not cancer, but they can still cause severe discomfort to the affected person.

This medicine is mainly for children who are 2 years or older and have tumors that doctors cannot remove with surgery. These tumors are called plexiform neurofibromas. Selumetinib was the first medicine approved to treat this condition.

On April 10, 2020, the Food and Drug Administration (FDA) approved Selumetinib for children with this condition. It was an important step because, before this, there were no approved treatments for these types of tumors in children. After Selumetinib's FDA approval, many people started using it.

Right now, Selumetinib is mostly used for children. Even though it is used mostly in children, researchers examine how Selumetinib for adults might treat other tumors. So, the list of uses for selumetinib may grow in the future.

How Does Selumetinib Work?

To understand how Selumetinib works, we must examine what happens in the body. People with neurofibromatosis type 1 have an alteration in their genes that causes certain body signals to go wrong. These signals tell cells when to grow. When these signals don’t work properly, cells can grow uncontrollably and form a huge, unusual mass of cells called a tumor.

The Selumetinib mechanism of action blocks a protein called MEK (mitogen-activated protein kinase). This protein is part of the signal that tells cells to grow. By stopping this protein, Selumetinib helps slow down or shrink the tumors. This can help reduce pain, swelling, and other symptoms caused by the tumors.

How to Start Selumetinib?

Selumetinib is a medicine that your doctor might give you if you have certain health conditions, like neurofibromatosis type 1 (NF1). It is not a regular medicine that you can buy from a shop; you can only get it if your doctor gives you a prescription. Before you start Selumetinib, your doctor will explain why you need it. They will also discuss its uses, side effects, and how it works in the body.

Taking the Medicine:

Selumetinib comes as a capsule. It should be taken by mouth with water. You must swallow the capsule whole. Do not open, break, chew, or crush it. You need to take it twice a day, about 12 hours apart. For example, if you take the first dose at 8 a.m., the second should be around 8 p.m. Selumetinib should be taken on an empty stomach. Do not eat 2 hours before and 1 hour after you take it. Always take Selumetinib at the same time every day. This helps the medicine work better and enables you to remember your doses.

What If You Vomit?

If you vomit after taking the capsule, do not take another one. Just wait and take the next dose at your regular time.

Dosing and Changes:

Your doctor will tell you the right Selumetinib dose for your condition. If you have side effects, the doctor may lower your dose or stop the medicine for some time. It is very important to tell your doctor if you feel unwell while taking Selumetinib. This helps the doctor decide what to do next.

What Are the Uses of Selumetinib?

Selumetinib is given to children who are 2 years old or older when the tumors cannot be removed with surgery. Selumetinib's uses mainly include the treatment of plexiform neurofibromas, which are soft lumps that grow under the skin or inside the body in people with NF1. These tumors are hard to remove with surgery, and Selumetinib is used when surgery is not possible. Sometimes, doctors may also study how it works in other age groups or conditions, but it is mostly used in children for this reason.

What Should I Know Before Using Selumetinib?

If your doctor has suggested Selumetinib, it is important to know a few things before you start. It is always best to be careful and informed before starting any treatment.

1. Talk to Your Doctor First:

Before using Selumetinib, tell your doctor if you are allergic to any medicines or if you have had bad reactions to any drug in the past. Also, show your doctor a list of all your medicines, supplements, vitamins, or herbal products. Some of these may not go well with Selumetinib. For example, vitamin E or St. John's wort may cause problems when taken with Selumetinib. So, do not start or stop any medicine without asking your doctor.

2. Health Problems You Should Mention

Let your doctor know if you have any eye problems, liver disease, heart disease, or swallowing problems. These conditions may affect how the medicine works for you. It is important for your safety.

3. If You Are Pregnant or Planning Pregnancy

If you are pregnant or plan to be, tell your doctor. Selumetinib may not be safe for the baby. You may need a pregnancy test before starting. Both men and women should use birth control during the treatment and for one week after stopping it. If pregnancy happens during treatment, contact your doctor right away.

Also, do not breastfeed while taking Selumetinib and for at least one week after your last dose.

What Is the Dosage of Selumetinib?

The usual dose of Selumetinib is based on the patient's body size. It is 25 milligrams per square meter of body surface area. This dose is taken twice a day. It should be taken on an empty stomach. This means not eating for 2 hours before and 1 hour after taking the medicine.

If a person has moderate liver problems, the dose should be lowered to 20 milligrams per square meter, twice daily. The safe dose for people with terrible liver problems is not known yet.

The capsules come in two strengths: 10 milligrams and 25 milligrams.

Missed Dose:

If you miss a dose of Selumetinib, take it as soon as you remember. But if it is less than 6 hours before your next dose, skip the missed one. Just wait and take your next dose at the usual time. Do not take two doses to make up for the missed one.

Overdose

Taking too much Selumetinib can be dangerous. If someone has signs like fainting or trouble breathing, get emergency help immediately. You can also call your local poison control center for help.

What Are the Side Effects of Selumetinib?

Before starting this medicine, it is good to know about its side effects. Like many other medicines, Selumetinib can cause changes in the body. Some of these changes are common and may not be very serious, but they can still make a person uncomfortable.

Here are the most common Selumetinib side effects:

• Vomiting.

• Rash on the skin.

• Pain in the belly.

• Loose motion or diarrhea.

• Feeling sick or nauseous.

• Dry skin.

• Feeling tired.

• Pain in the bones, muscles, or joints.

• Fever.

• Red or sore mouth (called stomatitis).

• Headache.

• Pain or swelling around the fingernails (called paronychia).

• Itching on the skin.

These side effects may happen when the body tries to get used to the medicine. Some people may have only a few of these, and others may have more. It is essential to tell the doctor if any side effects become hard to manage.

What Are the Precautions of Selumetinib?

Below are some simple precautions that people should follow when taking Selumetinib:

Heart Checkups Are Important:

Selumetinib can affect the heart. It may cause a problem called cardiomyopathy, where the heart becomes weak. So, doctors will check your heart before starting the medicine. Then, they will check it every few months. If a person’s heart function gets worse, the doctor may stop the medicine or reduce the dose. This is an important part of Selumetinib dosing.

Eye Checkups Are Needed:

Selumetinib may cause eye problems like blurry vision or other changes. People need to check their eyes before starting treatment and regularly after that. If serious eye issues happen, such as a blocked vein in the eye, the medicine may need to be stopped forever.

Tummy Troubles Like Diarrhea:

Some people may get diarrhea while taking Selumetinib. If that happens, taking medicine for diarrhea early and drinking extra fluids is good. If the problem worsens, the doctor might change the dose or stop the medicine.

Skin Problems:

Selumetinib can cause skin rashes. If the rash is bad, the doctor might lower the dose or stop the medicine.

Muscle Health:

This medicine can raise a chemical called creatine phosphokinase (CPK). High CPK can be a sign of muscle damage. Doctors will test for CPK before and during treatment. If levels go up, they will check for muscle issues and may pause the medicine.

Bleeding Risk from Vitamin E:

Selumetinib capsules contain vitamin E. Too much vitamin E can cause bleeding, so if someone is already taking other medicines that affect bleeding, like blood thinners, they need to be extra careful. The doctor will help manage this risk.

Watch for Selumetinib Side Effects

Common Selumetinib side effects include skin rash, diarrhea, nausea, and vision changes. Always tell the doctor about any new or worsening symptoms.

What Should You Know About Storage of Selumetinib?

It is very important to store Selumetinib properly so it stays safe and works well. This medicine should be kept in its original bottle. Do not move it to another container. Keep the bottle tightly closed when not in use.

Selumetinib should be stored at room temperature (20 °C to 25 °C (68 °F to 77 °F). Keep it away from heat, light, and moisture. Do not freeze the medicine. Do not store it in the bathroom because it is often warm and wet there.

There is a small packet inside the bottle called a desiccant. This helps keep the medicine dry. Do not take it out. Keep it in the bottle with the capsules. Also, always keep Selumetinib away from children and pets. Some bottles may look easy to open, and this can be dangerous. Make sure to keep the bottle in a place that is high and locked away.

Do not use old medicine or medicine that is no longer needed. If you do not know how to throw it away safely, ask your doctor or pharmacist. Knowing how to store Selumetinib is just one part of using it safely.

For Doctors

Indication:

Selumetinib is prescribed for treating neurofibromatosis type 1 (NF1) in children 2 years old with symptomatic, inoperable plexiform neurofibromas (PN).

Pharmacodynamics:

Selumetinib is a non-ATP-competitive mitogen-activated protein kinase kinase 1 and 2 inhibitor that can inhibit oncogenic downstream effects of the Raf-MEK-ERK signaling pathway, which is often considered overactive in some types of malignancies. A study on the impacts of Selumetinib in children with neurofibromatosis 1 found that the treatment with the antineoplastic resulted in a reduction in the tumor size of the malignancies. It was reported that there was a decrease in tumor-associated pain and improvements in the person's overall function.

Mechanism of Action:

The Ras-Raf-MEK-ERK signaling cascade is known to be activated in many cases of cancer and is responsible for the regulation of transcription of proteins involved in the process of apoptosis. Studies also proposed that mutations of the Raf component of the pathway can contribute to chemotherapy drug resistance. Ras and several kinases and phosphatases can regulate the Raf-MEK-ERK pathway. Often in cases of cancer, Ras, a G-protein receptor, is deregulated, allowing the downstream signaling to proceed unchecked. After many complex steps, Raf phosphorylates and MEK activates, which can then exert their effect on many downstream targets. The therapies that help to inhibit the upstream component of this pathway are demanding targets for cancer treatment.

Selumetinib exerts its effect by selectively stopping MEK 1 and MEK 2, which can then effectively blunt the pleiotropic effects of the Ras-Raf-MEK-ERK cascade. By inhibiting this oncogenic pathway, selimetinib reduces cell proliferation and promotes pro-apoptotic signal transduction.

Absorption:

According to several studies of Selumetinib at various doses in both pediatric and adult populations, the Tmax ranges between 1 hour and 1.5 hours. In healthy adults, the mean absolute value for bioavailability was reported as 62%. The drug is advised to be consumed on an empty stomach, as food can significantly decrease its concentration.

The Volume of Distribution: The mean volume of distribution of the drug Selumetinib in pediatric patients is between 78 L to 171 L.

Protein Binding Capacity: Studies investigating Selumetinib protein binding found that about 96 % of the Selumetinib was bound to serum albumin, whereas only less than 35 % was bound to alpha-1 acid glycoprotein. The overall concentration of Selumetinib, which is plasma protein-bound, is 98.4 %.

Metabolism:

Selumetinib is metabolized mostly in the liver, and the pathway is:

Hydrolysis of Selumetinib’s amide functional group produces M15, which contains carboxylic acid.

The primary amide is formed by eliminating the ethanediol moiety from the parent compound. Amide is known to hydrolyze M14 into M15 and glucuronide and further leads to oxidation of M14, leading to M2, M6, M1, M2, M6, and M1. The amide glucuronide M2 is considered a major circulating metabolite.

The demethylation of Selumetinib produces pharmacologically active M8, which, upon further oxidation, leads to M11. M8, on glucuronidation, produces M3 or M5 and then eliminates the ethanol moiety from M8, which may cause the primary amide.

The M8 (N-demethylated metabolite) accounts for less than 10 % of the circulating metabolites and can account for about 21 % to 35 % of any observed pharmacological activity.

Ribose conjugation is known to transform M12 into M9, whereas oxidation of M12 may lead to M10 and M13 metabolites. Glucuronidation of M10 produces M1.

Direct glucuronidation of Selumetinib produces M4 or M7, with M3 and M5 metabolites.

Route of Elimination: About 59 % of Selumetinib is eliminated in the feces, while almost 33 % is eliminated in the urine.

Half-Life of Selumetinib: Selumetinib has a short half-life. The elimination half-life associated with a 25 mg/m2 dose in pediatric patients is 6.2 hours. In other studies, it was estimated that 75 mg is administered twice, and the half-life is reported to be approximately 13 hours.

Clearance: Selumetinib's clearance in children is 8.8 L/hr. A study in healthy adult males found a clearance value of 15.7 L/hr.

Toxicity of Selumetinib: The information about the toxicity of Selumetinib is minimal and not readily available. Patients who are experiencing an overdose are at an increased risk of adverse effects like cardiomyopathy, ocular toxicity, and diarrhea.

What Are the Drug Interactions of Selumetinib?

It is important to know that Selumetinib can interact with other medicines. This means when you take Selumetinib with other drugs, it can change how the medicine works or may cause more side effects. These are called drug interactions. Knowing about drug interactions is important when using Selumetinib. It helps to get the most benefit from the medicine while lowering the chance of harm.

Some products can make Selumetinib side effects worse. For example, if you use products that have vitamin E in them along with Selumetinib, it might increase the chance of side effects.

Also, some drugs can make Selumetinib leave the body faster. When that happens, the medicine may not work as well. These include medicines like Rifampin, Rifabutin (used for infections), and drugs for seizures like Carbamazepine and Phenytoin. Even herbal products like St. John’s Wort can affect Selumetinib dosing and how the body handles the medicine.

Because of these risks, you should always tell your doctor about all the medicines you take. This includes other prescription drugs, over-the-counter drugs, and even herbal or vitamin products. Do not stop or change any medicine without asking your doctor.

Uses in Specific Populations:

Pregnancy: Animal studies show increased risks of fetal malformations and reduced fetal weight, even at doses lower than clinical exposure. Ensure pregnancy testing before starting treatment and advise patients about fetal risks.

Lactation: There is no human data, but Selumetinib is excreted in mouse milk and causes growth and developmental issues in pups. Advise against breastfeeding during treatment and at least one week after the last dose.

Females and Males of Reproductive Potential: Confirm negative pregnancy status before starting Selumetinib. Counsel both females and males (with partners of reproductive potential) to use effective contraception during treatment and for one week after stopping the drug.

Pediatric Use: This drug is approved for children older than two with NF1-related inoperable plexiform neurofibromas. Safety and efficacy are not established for children under two. Long-term animal data show growth plate issues at high doses.

Geriatric Use: No data are available on patients over 65.

Renal Impairment: No dose adjustment needed, including for patients with end-stage renal disease (ESRD).

Hepatic Impairment: Exposure increases in moderate or severe hepatic impairment. Reduce dose in moderate impairment (Child-Pugh B). No established dose for severe impairment (Child-Pugh C).

Conclusion

To wrap up, Selumetinib has opened new doors for children battling the challenges of neurofibromatosis type 1. As the first FDA-approved medicine for treating inoperable plexiform neurofibromas in children, it represents a medical milestone and a ray of hope for families seeking relief from a condition that once had no approved treatments. While it's not a cure, Selumetinib can significantly improve quality of life by shrinking tumors and reducing symptoms. And as researchers continue to study its potential in adults and other conditions, Selumetinib’s potential may be expanded. Staying informed, asking questions, and working closely with healthcare providers are the best ways to ensure safe and effective treatment with this miracle drug.

Key Takeaway/ Note From Icliniq

Neurofibromatosis can affect any child who carries the gene. But parents should not lose hope; talking to a healthcare provider can help you learn about treatment options that may comfort your child. If you’re anxious or unsure, you can speak to a doctor using the iCliniq online consultation platform. Whether it’s through chat, call, or video, help is just a tap away. All you need to do is pick up your phone and start consulting. Our expert doctors are ready to guide you with no long waiting times.